1. Field of the Invention
The present invention relates to a method, an apparatus and a program product for searching knots in wood-based material such as veneers or cut pieces cut from logs of wood or the like. For example, for manufacturing plywood, a log is cut using a cutting tool to consecutively obtain veneers with a thickness of several millimeters. The veneers are then cut to a predetermined size, and after drying, several veneers are integrated through lamination using an adhesive. During such manufacturing processes, it is necessary to sort (for instance, into five to seven grades) the veneers into those that will compose the outer layers of plywood, and those that will compose the inner layers according to degrees of positions, numbers and dimensions or the like of knots, unsound knots that have fallen out, cracks, and other defects such as discoloration due to mold or pitch that are found on the veneers. In other words, veneers are sorted to those with little or no aesthetic defects to be used as outer layers, and those that will comprise inner layers where such aesthetic defects, even if they exist in abundance, are irrelevant.
Conventionally, the process of sorting boards into those to be used as outer layers of plywood and those to be used as inner layers thereof has involved naked eye determination by a worker on veneers conveyed through a conveyer.
In addition, an example of a conventional method for automatically detecting defects in wood is described in Patent Document 1, wherein imperfections such as knots, cracks, rot and the like on the surfaces of wood to be laminated were detected using a linear television camera. This defect detection method involved determining defects to be removed based on whether color shading and the like of a detected surface exceed certain comparative judgment data.
Patent Document 1: Japanese Patent Laid-Open 8-145914
2. Description of the Related Art
The above-described conventional method had the following problems.
Naked eye determination led to inconsistencies from person to person (inaccuracy), and did not allow conveyor speed to be increased (low productivity).
In addition, since determination of defects using a linear television camera was solely based on color shading, there was a problem where configuration of knots, defects and the like could not be accurately detected.